Support is requested for a Keystone Symposia meeting entitled Positive-Strand RNA Viruses, organized by Raul Andino and Peter D. Nagy. The meeting will be held in Austin, Texas from May 1-5, 2016. Positive- strand RNA viruses, which are important and emerging human, animal and plant pathogens, cause significant harm to human health and major losses in agriculture. However, we still have a lot to learn about viral replication and virus-host interactions since (+)RNA viruses exploit host cells by recruiting host factors and escaping host antiviral responses. A major area of modern virology is to identify and dissect the functions of these host factors in virus replication with the ultimate goal of interferng with their virus promoting activities. Topics covered by this meeting include basic advances in research on viral replication structures, virus entry and virus evolution; virus-host interactions, discussed from the virus view on changing the host (including systems biology) and host responses and defense mechanisms; and emerging therapeutics. It is anticipated that rapidly emerging new concepts on virus-host interactions will help the participants to test various host factors for a large number of positive-strand RNA viruses to expand the arsenal of antiviral approaches. This meeting will bring together experts on positive-stranded RNA viruses that will facilitate the rapid progress and dissemination of new concepts in the complex field of virus-host interactions. Also, speakers who are expert with other groups of viruses will be invited to facilitate cross-talk with other areas in virology. Among the speakers will be interdisciplinary scientists (e.g., from the fields of virology, cell biology, genetics, evolution, macromolecular structures/assembly, systems biology and imaging) who would not normally meet with this group of researchers.